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A molar pregnancy occurs when tissue that would normally grow to become a fetus instead develops into a growth in the uterus. Molar pregnancies develop as a result of an abnormality of the placenta, which occurs during fertilization of the egg and sperm. Although there is no embryo, the growth in the uterus triggers symptoms of pregnancy.
Causes of Molar Pregnancy
There are two types of molar pregnancies. The first is called complete molar pregnancy. In complete molar pregnancy, sperm fertilizes an empty egg that contains no genetic information. The mass can grow into tissue, which often resembles a cluster of grapes, but it cannot develop into a fetus. Because the placenta will continue to grow, the pregnancy hormone hCG will be produced.
The second type of molar pregnancy is referred to as a partial molar pregnancy. In partial molar pregnancy, a normal egg is fertilized by two sperm. Instead of forming twins, something goes wrong and the mass develops into an abnormal embryo with too many chromosomes.
Rates of Molar Pregnancy
Molar pregnancy is an uncommon form of pregnancy loss. Approximately one out of every 1,000 women with early pregnancy symptoms will suffer from a molar pregnancy.
Risk Factors of Molar Pregnancy
Risk factors for molar pregnancy include a history of miscarriage and a history of molar pregnancy, especially if you have had two or more. The risk of complete molar pregnancy steadily increases after the age of 35. Women who eat a diet low in carotene, a form of vitamin A, also have a higher rate of complete molar pregnancy.
Signs of Molar Pregnancy
A molar pregnancy usually progresses like a normal, healthy pregnancy during the early weeks. However, around week 10, other symptoms begin to occur. These include vaginal bleeding, severe nausea and vomiting, rapid uterine growth, an uncomfortable feeling in the pelvis, and vaginal discharge of tissue shaped like grapes.
Molar pregnancies are diagnosed by a pelvic exam, a blood test to measure pregnancy hormones, and a pelvic ultrasound. They can also be discovered during a routine ultrasound early in pregnancy.
Complications of Molar Pregnancy
Along with causing heavy uterine bleeding, molar pregnancy can also cause gestational trophoblastic disease, a growth of abnormal tissue during pregnancy. This tissue can continue to grow after the mole has been removed, though it is rare. Of 1,000 cases of complete molar pregnancy, 150 to 200 women will develop trophoblastic disease in which the tissue keeps growing. For every 1,000 cases of partial molar pregnancy, only 50 women will develop trophoblastic disease.
In a few cases, cancer can develop as a result of the trophoblastic disease, though most women who develop this cancer are cured with treatment.
Treatment for Molar Pregnancy
Once a molar pregnancy has been diagnosed, treatment is needed immediately to remove the growth from the uterus. The surgical treatment to remove the growth is called dilation and curettage (D&C).
After the mole has been removed, you will have regular blood tests over the next six to 12 months to check for signs of trophoblastic disease. A woman who has had a molar pregnancy is recommended to wait six months to one year before becoming pregnant, since pregnancy would make it difficult to monitor hCG levels.
Usually, trophoblastic disease does not prohibit most women from becoming pregnant in the future.